Culture Note for the month – Orchid nutrition
Dr. K.S.Shashidhar
Just look at nature how orchids latch on to the branches, crevices and sometimes on the tree tops exposed to harsh weather conditions and at times almost arid and with their roots clinging and dangling in the air, they get some nutrition through the collected biomass such as leaf litter, bird droppings and the rain water which provide little quantity of nutrients. Orchids being perennial and slow growing plants, they derive their nutrition requirement during their growth season mainly during the vegetative growth. Orchids are known to live and grow for longer periods without artificially supplementing any fertilizers but giving them low doses on a continuous basis during active growth stages will not only enable them to produce quality blooms but stronger and good vegetative growth which helps in better pest and disease tolerance. Especially, when they are brought out from its natural growing conditions and grown artificially at home in different media, the plant needs some kind of nutrition supplement.
When growers started culturing orchids, they used both organic and inorganic materials.Inorganic materials like charcoal, Brickbats, LECA, lava rock, perlite though provide appropriate aeration, drainage but do not support any nutrition. Whereas organic materials like osmunda fern blocks (tree fern), bark pieces, Coconut Husk Chips and other organic material sustain the plants with small quantities of nutrition. Over a period of time, organic materials like tree fern blocks and even bark is declining making its availability difficult both in terms of quantity and quality. Growers started mixing both organic and inorganic materials which are locally available.
Orchid nutrition is a relatively old field when experiments on orchid nutrition started as back as in 1946 with application of dilute nitrogen solution to the plants and kept on trying different doses till desirable results were obtained. It was well known information that orchids are slow growing and need nutrients in smaller proportions. This was provided when grown in organic media probably the decomposing process will provide this nutrition in a slow but steady manner. The response of orchid plants was interesting to this nutrition supplement evident in terms of the quantity and quality of flowers even when they were grown in organic media. Organic media such as tree fern blocks and tree bark materials will contain Nitrogen and during the course of its decomposition the Nitrogen from these media will be utilized by the decomposing organisms rendering the media deficient in Nitrogen (concept of C: N ratio). Most of the growers use a balanced fertilizer of NPK and in addition some trace elements and all these depend on what type of media is being used to grow orchids. It is also important that what form of Nitrogen is being made available to the plant whether Nitrate, ammoniacal or urea. The best would be the first two types as the urea form will damage the orchids when grown in inorganic material.
Over feeding with fertilizers
Overfeeding of fertilizers does more harm than under feeding the orchids
- If overfeeding does not kill the plants definitely it will make them weak and have negative impact on its growth and flowering
- The plants may produce many shoots (vegetative growth) and somewhat fragile growth (too much of Nitrogen) and no flowers
- The roots may tend to burn and die
- As many orchids even when they are mature still continue to have a symbiotic association with the mycorrhiza ( as seen in paphiopedilums), overdose may be harmful
- Of the 16 elements required by any plant including orchids, Carbon, Hydrogen and Oxygen are already provided by nature. Among the other major nutrients Nitrogen (for vegetative growth), Phosphorus and Potassium (for flowering and other reproductive activities) are important. Among the secondary nutrients, Calcium, Magnesium and Sulphur play very important role and needs to be provided in smaller quantities.
Growers have been using fertilizer mixtures with other trace elements such as iron, Manganese, Copper, Zinc, Boron, Molybdenum, coupled with this some are using vitamins and hormones. Though all these are required, one has to be careful in providing them in low quantities as over dose (over enthusiasm) will result in interactive mechanism rendering non availability of other nutrients and sometimes have deleterious effects.
Growers have also been using many organic sources (for fertilizing orchids) such as fish emulsion, bone meal, cowdung manure, chicken manure, the problem is you need larger quantities of these to supply lower percentage of nutrients and especially under pot culture, it may pose a problem. In addition when these organic fertilsers are applied to orchids in pots they may be washed off or drained off because of the media, but still there are many advantages of using these.
Happy Orchid growing